You're seeing this page as if you were . The main menu is still yours, though. Exit from immersion
Zakhar GulchakZG

Zakhar Gulchak

Senior FullStack Engineer | Node.JS Python React

350 €/día
Lisbon, PT
8-15 años

Tiempo medio de respuesta: 1h

Acerca de Zakhar

Senior Full-Stack Engineer with 15 years building high-performance web and mobile applications across e-commerce, healthtech, fintech, and adtech. Core stack: React (8+ yrs), TypeScript, Node.js (6+ yrs), Python (FastAPI — production project shipped), and React Native (Expo).

I actively integrate AI development tools (Claude Code and similar) into my workflow, gaining measurable speed and flexibility across prototyping, debugging, and delivery.

Proven at both team delivery and solo end-to-end execution — I've driven architecture decisions on monorepos and federated GraphQL, and independently shipped production services, mobile apps, and side projects. Infrastructure experience spans Docker, Kubernetes (production), AWS, GCP, Terraform, and cost-effective fly.io + SQLite + Litestream setups.

Learning Python, preparing for AWS Solutions Architect certification. Former lecturer at Kyiv Polytechnic (3 course streams, 200+ students).
  • Inglés

    Competencia profesional completa

  • Ucraniano

    Bilingüe o nativo

  • Ruso

    Bilingüe o nativo

  • Alemán

    Nociones

  • Portugués

    Nociones

Acepta trabajo presencial
Lisbon (hasta 50 km)

Experiencia

  • PelagoApps
    Senior FullStack Engineer
    SALUD & BIENESTAR
    agosto de 2025 - octubre de 2025 (2 meses)
    Lisbon, Portugal
    • • Developed features for AI HealthTech mobile applications using React Native, TypeScript, and Firebase/Firestore backend.
    • • Implemented analytics infrastructure (Firebase Analytics, BigQuery) and third-party integrations (OneSignal, Adjust).
    • • Integrated LangChain/LangSmith for AI-powered health recommendations, working on prompt engineering and model interaction flows.
    React Native Typescript Langchain Firebase BigQuery
  • Aignostics GmbH
    Senior Fullstack Engineer
    noviembre de 2023 - noviembre de 2024 (1 año)
    Berlin, Germany
    • • Built and optimized UI components handling complex data visualization for pathology workflows, supporting datasets with 2,000+ slides and enabling real-time interactions for clinical users.
    • • Refactored the entire application routing system, resolving over 10 persistent navigation and breadcrumb issues, which led to a 20% drop in user-reported bugs across two release cycles.
    • • Designed and implemented a robust integration testing approach that simulates real user navigation via the router. This caught 10+ critical bugs before they hit the main branch, preventing regressions and improving release confidence.
    • • Built a comprehensive test suite (React Testing Library, Cypress) covering 20+ routing paths and key pages, significantly reducing QA bottlenecks and increasing automated test coverage by 35%.
    • • Architected performance optimizations for data-heavy onboarding module, scaling from 100 to 2,000+ slides while maintaining smooth UX, improving load times by 60% and enabling support for enterprise clients.
    • • Fixed over 50 UI and API bugs ofvarying criticality — both proactively and reactively — improving product polish and easing developer handover between sprints.
    • • Unified and modernized the TypeScript build setup across the monorepo. This led to a 40% faster CI job runtime and improved DX for all team members working in the shared codebase.
    • • Led architectural discussions and design reviews, serving as technical lead for frontend decisions on routing, testing, and performance optimization.
    Typescript React.js Node.js Python Google cloud
  • N-iX -forBWT
    Senior FullStack Engineer
    noviembre de 2022 - noviembre de 2023 (1 año)
    Kyiv, Ukraine, 02000
    • • Refactored component library for better performance and maintainability.
    • • Led the transition to Federated GraphQL across microservices, reducing average query response time by 40% and improving data modularity for 3 frontend subteams.
    • • Unified architecture across owned apps; introduced shared patterns and documentation.
    • • Enhanced CI/CD pipeline with pre-commit hooks, automated linting, and unit tests, reducing main branch issues by 25%.
    Node.js React Native

Recomendaciones

Sé el primero en recomendar a Zakhar

Ayuda a este freelance a destacar compartiendo tu experiencia.

Estos perfiles de freelance también coinciden con tus criterios

AgathaA

Agatha Frydrych

Backend Java Software Engineer

4.7

(3)

2

BaptisteB

Baptiste Duhen

Fullstack developer

4.6

(4)

5

AmedA

Amed Hamou

Senior Lead Developer

4

(2)

7

AudreyA

Audrey Champion

Web developer

4.3

(3)

4

Formación

  • Master's degree in Information Control Systems
    Donetsk National Technical University
    2009
    Master's degree in Information Control Systems

Certificados

Conjunto de habilidades profesionales

Categorías